How to ignore parent tag from json??
Here is my json
String str = "{\"parent\": {\"a\":{\"id\": 10, \"name\":\"Foo\"}}}";
And here is the class to be mapped from json.
public class RootWrapper {
private List<Foo> foos;
public List<Foo> getFoos() {
return foos;
}
@JsonProperty("a")
public void setFoos(List<Foo> foos) {
this.foos = foos;
}
}
Here is the test
public class JacksonTest {
@Test
public void wrapRootValue() throws Exception {
ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationConfig.Feature.UNWRAP_ROOT_VALUE, true);
mapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
String str = "{\"parent\": {\"a\":{\"id\": 10, \"name\":\"Foo\"}}}";
RootWrapper root = mapper.readValue(str, RootWrapper.class);
Assert.assertNotNull(root);
}
I get the error ::
org.codehaus.jackson.map.JsonMappingException: Root name 'parent' does not match expected ('RootWrapper') for type [simple type, class MavenProjectGroup.mavenProjectArtifact.RootWrapper]
I found the solution given by Jackson annotation::
(a) Annotate you class as below
@JsonRootName(value = "parent")
public class RootWrapper {
(b) It will only work if and only if ObjectMapper is asked to wrap.
ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationConfig.Feature.UNWRAP_ROOT_VALUE, true);
Job Done!!
Another hiccup with Jackson way of Deserialization 🙁
if 'DeserializationConfig.Feature.UNWRAP_ROOT_VALUE configured', it unwrap all jsons, eventhough my class in not annotated with @JsonRootName(value = "rootTagInJson"), isn't weired.
I want to unwrap root tag only if the class is annotated with @JsonRootName otherwise, don't unwrap.
So below is the usecase for unwrap root tag.
###########################################################
Unwrap only if the class is annotated with @JsonRootName.
############################################################
I did a small change in ObjectMapper of Jackson source code and created a new version of jar.
1. Place this method in ObjectMapper
// Ash:: Wrap json if the class being deserialized, are annotated
// with @JsonRootName else do not wrap.
private boolean hasJsonRootName(JavaType valueType) {
if (valueType.getRawClass() == null)
return false;
Annotation rootAnnotation = valueType.getRawClass().getAnnotation(JsonRootName.class);
return rootAnnotation != null;
}
2. Edit ObjectMapper method ::
Replace
cfg.isEnabled(DeserializationConfig.Feature.UNWRAP_ROOT_VALUE)
with
hasJsonRootName(valueType)
3. Build your jar file and use it.
Best Answer
An example taken from TestRootName.java in https://github.com/FasterXML/jackson-databind may give a better way of doing this. Specifically using withRootName(""):